At present OLED has been used in many applications such as car display devices, game players, PDAs, mobile phones, and the like. Displaying contents generally include pictures and characters composed of pixels. Refer to FIG. 1A for a conventional OLED display device including a driver circuit diagram for a passive and an active OLED. The driver circuit is built in a driver chip 10 to drive a plurality of pictures 12, 13, 14, 15, and 16 and a plurality of pixels 17 located on a display panel 11.The driver chip 10 outputs current signals through data lines 100 and scanning signals through scanning lines 101 to provide a constant electric current to drive the pictures and pixels. As the driver circuit shown in FIG. 1A supplies a constant electric current, the larger picture will have a dimmer luminosity while the smaller picture will has a stronger luminosity. As a result, the whole display picture has an uneven luminosity.
Refer to FIG. 1B for the driver circuit diagram of another conventional OLED display device. It is an improved circuit over the one shown in FIG. 1A. It has another driver chip 18 to provide a greater electric current to the pictures 12, 13, 14, 15 and 16 to remedy the dimmer luminosity problem occurred to larger display pictures. However, the addition of an extra driver chip increases the cost. Moreover, more signal lines are needed, and more line configuration space is required on the display panel.